1. Technical Field
The present invention relates to spectrum analyzers, and in particular to a frequency extension module for microwave and millimeter wave spectrum analyzers.
2. Related Art
Spectrum analyzers are well-known tools which can be used, among other functionality, to determine the composition of various input signals and waveforms. These analyzers can be provided in a variety of form factors from large, stand alone lab equipment to relatively compact portable devices. Spectrum analyzers generally offer a limited bandwidth over which they are operable to analyze input signals.
FIG. 1 shows a prior art spectrum analyzer. As shown in FIG. 1, RF input signals, having frequencies within the bandwidth of the spectrum analyzer are received at RF IN 100. The input signal is processed through switching block 102, multiple channel filters and amps block 104, switching block 106 to the multiple mixers block 108. The processed signal is mixed with local oscillator (LO) signals 110 before being passed to an A-to-D converter 112 after which the results are shown in display 114. Additionally, the spectrum analyzer can be controlled using processor 118. Any signals received outside of the operable bandwidth of the spectrum analyzer will not be analyzed.
FIG. 2 shows a prior art system which provides harmonic mixer frequency extension. As shown in FIG. 2, the frequency of range of the spectrum analyzer 200 can be extended using a harmonic mixer 202 and a diplexer 204. The harmonic mixer has a separate input port 206 from the normal RF input 208 of the spectrum analyzer. The diplexer receives LO signals from the spectrum analyzer which are then mixed at the harmonic mixer with the input signal from input port 206. The resulting IF are then passed back through the diplexer to the spectrum analyzer. Such prior art systems have a number of drawbacks. For example, the system shown in FIG. 2 requires two inputs, and therefore does not allow full band spectral analysis coming from one signal source. Additionally, the use of a harmonic mixer can result in higher conversion loss.